This study concerns the father's role in his adolescent son's use of tobacco and marijuana. The study has two foci: (1) A specification of paternal factors (paternal personality/attitudinal attributes, paternal child-rearing practices, and the extent to which the father serves as a role model for his son) which may influence his son's drug behavior and (2) An interrelationship approach which requires examination not only of the paternal dimensions alone but in interaction with the adolescent's own personality and the family system. The paternal factors alone and in interaction will be examined in relation to the son's (a) choice of drugs and (b) mild versus heavy use of tobacco and marijuana. The sample consists of 250 male adolescents and their fathers. Self-administered questionnaires were given in the Fall of 1979 and Spring of 1980. The significance of the study lies in its attempt to examine a greatly underresearched area--the role of the father in his son's drug behavior. Such a study is necessary to help balance the research which already exists on maternal, peer, and personality factors related to drug use.